> I think it's because they're carefully managing their persona in each group This is a great point. If that's the root cause the cratering makes sense, it's

> I think it's because they're carefully managing their persona in each group This is a great point. If that's the root cause the cratering makes sense, it's (scientifically) known that the most stable relationships exist between two people who have one or a few friends in common but who introduce subsets of friend groups to each other.